So no judge in a court of arbitration will ever be called to read sentence in the case of Lance Armstrong. But for anyone with eyes to see and ears to hear, the jury was never out.

By refusing to mount a defence in the US Anti-Doping Agency's case against him, Lance Armstrong has – whatever equivocation and claims of persecution he persists in – all but conceded that he won his seven Tour de France titles by doping. And by walking away from a defence he has ceded those yellow jerseys and lost his status as the most remarkable serial winner in the history of the sport.

There may be some small fraternity of true believers who still need the master-narrative of the heroic cancer survivor-turned-sports superstar and still cling to a conviction that he could have beaten the rap if the world had not conspired against him.

Armstrong's statement repeats a familiar litany of disingenuous indignation – his record of wins, a lack of physical evidence, the "nonsense" of this "witch-hunt" and so on – but by this decision, Armstrong has excommunicated himself from the Church of Lance: he no longer believes in the plausibility of his own denials. The aggression that kept accusers in check and witnesses silent for so long has been replaced by weariness and resignation.

"There comes a point in every man's life when he has to say, 'Enough is enough.' For me, that time is now," his statement reads.

Yet even a dope cheat still needs to be a master tactician to win the Tour de France: if Armstrong decided to quit the fight it was because this was the least worst option remaining to him. This pre-emptive retreat allows him to avoid the formal process of prosecution and conviction, and the humiliation that would have gone along with that. Perhaps his Livestrong foundation, and what remains of his tarnished brand, can thus survive in some netherworld of unreason.

Where does that leave cycling? With many unresolved questions. We may never know who were all the former team-mates of Armstrong that USADA had ready to testify against him about the years of EPO use, steroids, blood-doping techniques and whatever else that delivered that unbroken string of Tour victories, though we can guess at their identities. And we will have to wait and see whether Armstrong's longtime team manager, Johan Bruyneel, will attempt a defence, though the percentage must be in his folding quietly and taking a ban.

We may never finally know what deals were done to hush up the alleged positive tests Armstrong gave, though we have our suspicions. And we can only wonder who might now be deemed to have won the Tour de France from 1999 to 2005, though we must assume that the Tour authorities would rather award no result than attempt the fool's errand of seeking retrospectively a clean cyclist in the top 10 of any of those years.

Better to look forward and learn. There is no doubt that the anti-doping agencies have won the upper hand since Lance Armstrong's heyday in the fight to rid the sport of performance-enhancing drugs. Many do still cheat, though they are fewer and more are caught. Teams keep sponsors by staying clean; they lose them when riders are discovered doping. The governing body, the UCI, has abandoned its shameful connivance of the EPO era.

But there's no reason for complacency. It will only take a tangential advance in medical science for some new substance to become available for which there is no test; then the cheats will be ahead in the pharmacological arms race once more.

The most important lesson of the Lance Armstrong story, though, is the hardest to prepare for and guard against: our own gullibility and willing complicity. What is astounding and disturbing is that one man – a dominant personality as well as a dominant athlete – was able to enforce his will, isolate, bully and silence his doubters and critics, and win the world's top cycling event year after year and make people believe in him, despite there being, apparently, dozens of witnesses to its utter phoniness. Too many people had too much invested in the Lance Armstrong story, and the power of persuasion followed the money.

The moral of the story is that if a cyclist looks too good to be true, then he probably is. But if a cyclist looks too good to be true and has an entourage of lawyers, press flaks, doctors and bodyguards, then he definitely is.